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1169 lines
39 KiB
Text
INTERNET-DRAFT D.R.T. Robinson
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<draft-robinson-www-interface-01.txt <./draft-robinson-www-interface-01.txt>> University of Cambridge
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Expires 15 August 1996 15 February 1996
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The WWW Common Gateway Interface Version 1.1
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Status of this memo
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This document is an Internet-Draft. Internet-Drafts are working
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documents of the Internet Engineering Task Force (IETF), its areas
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and its working groups. Note that other groups may also distribute
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working documents as Internet-Drafts.
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Internet-Drafts are draft documents valid for a maximum of six months
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and may be updated, replaced or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
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material or to cite them other than as `work in progress'.
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To learn the current status of any Internet-Draft, please check the
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`1id-abstracts.txt' listing contained in the Internet-Drafts Shadow
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Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
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munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
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ftp.isi.edu (US West Coast).
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Distribution of this document is unlimited. Please send comments to
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the author; general discussion about CGI should take place on the
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<www-talk@w3.org> mailing list.
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Abstract
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The Common Gateway Interface (CGI) is a simple interface for running
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external programs, software or gateways under an information server
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in a platform-independent manner. Currently, the supported
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information servers are HTTP servers.
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The interface has been in use by the World-Wide Web since 1993. This
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specification defines the interface known as `CGI/1.1', and its use
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on the Unix(R) and AmigaDOS(tm) systems.
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1 <#section-1>. Introduction
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1.1 <#section-1.1>. Purpose
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Together the HTTP [3 <#ref-3>] server and the CGI script are responsible for
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servicing a client request by sending back responses. The client
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request comprises a Universal Resource Identifier (URI) [1 <#ref-1>], a
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request method and various ancillary information about the request
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provided by the transport mechanism.
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Robinson [Page 1]
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<#page-2>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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The CGI defines the abstract parameters, known as environment
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variables, which describe the client's request. Together with a
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concrete programmer interface this specifies a platform-independent
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interface between the script and the HTTP server.
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1.2 <#section-1.2>. Requirements
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This specification uses the same words as RFC 1123 <./rfc1123> [5 <#ref-5>] to define the
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significance of each particular requirement. These are:
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must
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This word or the adjective `required' means that the item is an
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absolute requirement of the specification.
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should
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This word or the adjective `recommended' means that there may
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exist valid reasons in particular circumstances to ignore this
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item, but the full implications should be understood and the case
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carefully weighed before choosing a different course.
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may
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This word or the adjective `optional' means that this item is
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truly optional. One vendor may choose to include the item because
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a particular marketplace requires it or because it enhances the
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product, for example; another vendor may omit the same item.
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An implementation is not compliant if it fails to satisfy one or more
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of the `must' requirements for the protocols it implements. An
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implementation that satisfies all of the `must' and all of the
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`should' requirements for its features is said to be `unconditionally
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compliant'; one that satisfies all of the `must' requirements but not
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all of the `should' requirements for its features is said to be
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`conditionally compliant'.
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1.3 <#section-1.3>. Specifications
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Not all of the functions and features of the CGI are defined in the
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main part of this specification. The following phrases are used to
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describe the features which are not specified:
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system defined
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The feature may differ between systems, but must be the same for
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different implementations using the same system. A system will
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usually identify a class of operating-systems. Some systems are
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Robinson [Page 2]
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<#page-3>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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defined in section 12 <#section-12> of this document. New systems may be defined
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by new specifications without revision of this document.
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implementation defined
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The behaviour of the feature may vary from implementation to
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implementation, but a particular implementation must document its
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behaviour.
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1.4 <#section-1.4>. Terminology
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This specification uses many terms defined in the HTTP/1.0
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specification [3 <#ref-3>]; however, the following terms are used here in a
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sense which may not accord with their definitions in that document,
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or with their common meaning.
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environment variable
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A named parameter that carries information from the server to the
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script. It is not necessarily a variable in the operating-system's
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environment, although that is the most common implementation.
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script
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The software which is invoked by the server via this interface. It
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need not be a standalone program, but could be a
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dynamically-loaded or shared library, or even a subroutine in the
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server.
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server
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The application program which invokes the script in order to
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service requests.
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2 <#section-2>. Notational Conventions and Generic Grammar
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2.1 <#section-2.1>. Augmented BNF
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All of the mechanisms specified in this document are described in
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both prose and an augmented Backus-Naur Form (BNF) similar to that
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used by RFC 822 <./rfc822> [6 <#ref-6>]. This augmented BNF contains the following
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constructs:
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name = definition
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The name of a rule is simply the name itself; it is separated from
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the definition by the equal character ("="). Whitespace is only
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significant in that continuation lines of a definition are
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Robinson [Page 3]
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<#page-4>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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indented.
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"literal"
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Quotation marks (") surround literal text, except for a literal
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quotation mark, which is surrounded by angle-brackets ("<" and
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">"). Unless stated otherwise, the text is case-sensitive.
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rule1 | rule2
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Alternative rules are separated by a vertical bar ("|").
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(rule1 rule2 rule3)
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Elements enclosed in parentheses are treated as a single element.
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*rule
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A rule preceded by an asterisk ("*") may have zero or more
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occurrences. A rule preceded by an integer followed by an asterisk
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must occur at least the specified number of times.
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[rule]
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A element enclosed in square brackets ("[" and "]") is optional.
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2.2 <#section-2.2>. Basic Rules
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The following rules are used throughout this specification to
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describe basic parsing constructs.
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alpha = lowalpha | hialpha
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lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h"
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| "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p"
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| "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x"
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| "y" | "z"
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hialpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H"
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| "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P"
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| "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X"
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| "Y" | "Z"
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digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7"
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| "8" | "9"
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OCTET = <any 8-bit byte>
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CHAR = <any character>
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CTL = <any control character>
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SP = <space character>
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NL = <newline>
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LWSP = SP | NL | <horizontal-tab>
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Robinson [Page 4]
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<#page-5>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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tspecial = "(" | ")" | "@" | "," | ";" | ":" | "\" | <">
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| "/" | "[" | "]" | "?" | SP
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token = 1*<any CHAR except CTLs or tspecials>
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quoted-string = ( <"> *qdtext <"> ) | ( "<" *qatext ">")
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qdtext = <any CHAR except <"> and CTLs but including LWSP>
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qatext = <any CHAR except "<", ">" and CTLs but
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including LWSP>
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Note that newline (NL) need not be a single character, but can be a
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character sequence.
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3 <#section-3>. URL Encoding
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Some variables and constructs used here are described as being
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`URL-encoded'. This encoding is described in section 2.2 of RFC 1738 <./rfc1738#section-2.2>
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[4 <#ref-4>]. In a URL encoded string an escape sequence consists of a percent
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character ("%") followed by two hexadecimal digits, where the two
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hexadecimal digits form an octet. An escape sequence represents the
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graphic character which has the octet as its code within the US-ASCII
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[11 <#ref-11>] coded character set, if it exists. If no such graphic character
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exists, then the escape sequence represents the octet value itself.
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Note that some unsafe characters may have different semantics if they
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are encoded. The definition of which characters are unsafe depends on
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the context.
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4 <#section-4>. The Script URI
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A `Script URI' can be defined; this describes the resource identified
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by the environment variables. Often, this URI will be the same as the
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URI requested by the client (the `Client URI'); however, it need not
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be. Instead, it could be a URI invented by the server, and so it can
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only be used in the context of the server and its CGI interface.
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The script URI has the syntax of generic-RL as defined in section 2.1
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of RFC 1808 <./rfc1808#section-2.1> [7 <#ref-7>], with the exception that object parameters and
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fragment identifiers are not permitted:
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<scheme>://<host>:<port>/<path>?<query>
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The various components of the script URI are defined by some of the
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environment variables (see below);
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script-uri = protocol "://" SERVER_NAME ":" SERVER_PORT enc-script
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enc-path-info "?" QUERY_STRING
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where `protocol' is found from SERVER_PROTOCOL, `enc-script' is a
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URL-encoded version of SCRIPT_NAME and `enc-path-info' is a
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Robinson [Page 5]
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<#page-6>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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URL-encoded version of PATH_INFO.
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5 <#section-5>. Environment variables
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Environment variables are used to pass data about the request from
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the server to the script. They are accessed by the script in a system
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defined manner. In all cases, a missing environment variable is
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equivalent to a zero-length (NULL) value, and vice versa. The
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representation of the characters in the environment variables is
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system defined.
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Case is not significant in the names, in that there cannot be two
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different variable whose names differ in case only. Here they are
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shown using a canonical representation of capitals plus underscore
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("_"). The actual representation of the names is system defined; for
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a particular system the representation may be defined differently to
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this.
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The variables are:
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AUTH_TYPE
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CONTENT_LENGTH
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CONTENT_TYPE
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GATEWAY_INTERFACE
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HTTP_*
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PATH_INFO
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PATH_TRANSLATED
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QUERY_STRING
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REMOTE_ADDR
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REMOTE_HOST
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REMOTE_IDENT
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REMOTE_USER
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REQUEST_METHOD
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SCRIPT_NAME
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SERVER_NAME
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SERVER_PORT
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SERVER_PROTOCOL
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SERVER_SOFTWARE
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AUTH_TYPE
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This variable is specific to requests made with HTTP.
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If the script URI would require access authentication for external
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access, then this variable is found from the `auth-scheme' token
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in the request, otherwise NULL.
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AUTH_TYPE = "" | auth-scheme
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Robinson [Page 6]
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<#page-7>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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auth-scheme = "Basic" | token
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HTTP access authentication schemes are described in section 11 <#section-11> of
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the HTTP/1.0 specification [3 <#ref-3>]. The auth-scheme is not
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case-sensitive.
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CONTENT_LENGTH
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The size of the entity attached to the request, if any, in decimal
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number of octets. If no data is attached, then NULL. The syntax is
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the same as the HTTP Content-Length header (section 10 <#section-10>, HTTP/1.0
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specification [3 <#ref-3>]).
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CONTENT_LENGTH = "" | [ 1*digit ]
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CONTENT_TYPE
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The Internet Media Type [9 <#ref-9>] of the attached entity. The syntax is
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the same as the HTTP Content-Type header.
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CONTENT_TYPE = "" | media-type
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media-type = type "/" subtype *( ";" parameter)
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type = token
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subtype = token
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parameter = attribute "=" value
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attribute = token
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value = token | quoted-string
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The type, subtype and parameter attribute names are not
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case-sensitive. Parameter values may be case sensitive. Media
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types and their use in HTTP are described section 3.6 <#section-3.6> of the
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HTTP/1.0 specification [3 <#ref-3>]. Example:
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application/x-www-form-urlencoded
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There is no default value for this variable. If and only if it is
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unset, then the script may attempt to determine the media type
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from the data received. If the type remains unknown, then
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application/octet-stream should be assumed.
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GATEWAY_INTERFACE
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The version of the CGI specification to which this server
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complies. Syntax:
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GATEWAY_INTERFACE = "CGI" "/" 1*digit "." 1*digit
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Note that the major and minor numbers are treated as separate
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Robinson [Page 7]
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<#page-8>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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integers and that each may be incremented higher than a single
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digit. Thus CGI/2.4 is a lower version than CGI/2.13 which in
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turn is lower than CGI/12.3. Leading zeros must be ignored by
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scripts and should never be generated by servers.
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This document defines the 1.1 version of the CGI interface.
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HTTP_*
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These variables are specific to requests made with HTTP.
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Interpretation of these variables may depend on the value of
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SERVER_PROTOCOL.
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Environment variables with names beginning with "HTTP_" contain
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header data read from the client, if the protocol used was HTTP.
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The HTTP header name is converted to upper case, has all
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occurrences of "-" replaced with "_" and has "HTTP_" prepended to
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give the environment variable name. The header data may be
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presented as sent by the client, or may be rewritten in ways which
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do not change its semantics. If multiple headers with the same
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field-name are received then they must be rewritten as a single
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header having the same semantics. Similarly, a header that is
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received on more than one line must be merged onto a single line.
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The server must, if necessary, change the representation of the
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data (for example, the character set) to be appropriate for a CGI
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environment variable.
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The server is not required to create environment variables for all
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the headers that it receives. In particular, it may remove any
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headers carrying authentication information, such as
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"Authorization"; it may remove headers whose value is available to
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the script via other variables, such as "Content-Length" and
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"Content-Type".
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PATH_INFO
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A path to be interpreted by the CGI script. It identifies the
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resource or sub-resource to be returned by the CGI script. The
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syntax and semantics are similar to a decoded HTTP URL `hpath'
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token (defined in RFC 1738 <./rfc1738> [4 <#ref-4>]), with the exception that a
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PATH_INFO of "/" represents a single void path segment. Otherwise,
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the leading "/" character is not part of the path.
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PATH_INFO = "" | "/" path
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path = segment *( "/" segment )
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segment = *pchar
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pchar = <any CHAR except "/">
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Robinson [Page 8]
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<#page-9>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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The PATH_INFO string is the trailing part of the <path> component
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of the script URI that follows the SCRIPT_NAME part of the path.
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PATH_TRANSLATED
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The OS path to the file that the server would attempt to access
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were the client to request the absolute URL containing the path
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PATH_INFO. i.e for a request of
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protocol "://" SERVER_NAME ":" SERVER_PORT enc-path-info
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where `enc-path-info' is a URL-encoded version of PATH_INFO. If
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PATH_INFO is NULL then PATH_TRANSLATED is set to NULL.
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PATH_TRANSLATED = *CHAR
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PATH_TRANSLATED need not be supported by the server. The server
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may choose to set PATH_TRANSLATED to NULL for reasons of security,
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or because the path would not be interpretable by a CGI script;
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such as the object it represented was internal to the server and
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not visible in the file-system; or for any other reason.
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The algorithm the server uses to derive PATH_TRANSLATED is
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obviously implementation defined; CGI scripts which use this
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variable may suffer limited portability.
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QUERY_STRING
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A URL-encoded search string; the <query> part of the script URI.
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QUERY_STRING = query-string
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query-string = *qchar
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qchar = unreserved | escape | reserved
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unreserved = alpha | digit | safe | extra
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reserved = ";" | "/" | "?" | ":" | "@" | "&" | "="
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safe = "$" | "-" | "_" | "." | "+"
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extra = "!" | "*" | "'" | "(" | ")" | ","
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escape = "%" hex hex
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hex = digit | "A" | "B" | "C" | "D" | "E" | "F" | "a"
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| "b" | "c" | "d" | "e" | "f"
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The URL syntax for a search string is described in RFC 1738 <./rfc1738> [4 <#ref-4>].
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REMOTE_ADDR
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The IP address of the agent sending the request to the server. Not
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necessarily that of the client.
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Robinson [Page 9]
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<#page-10>
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INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
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REMOTE_ADDR = hostnumber
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hostnumber = digits "." digits "." digits "." digits
|
|
digits = 1*digit
|
|
|
|
REMOTE_HOST
|
|
|
|
The fully qualified domain name of the agent sending the request
|
|
to the server, if available, otherwise NULL. Not necessarily that
|
|
of the client. Fully qualified domain names take the form as
|
|
described in section 3.5 of RFC 1034 <./rfc1034#section-3.5> [8 <#ref-8>] and section 2.1 of RFC <./rfc1123>
|
|
1123 <./rfc1123> [5 <#ref-5>]; a sequence of domain labels separated by ".", each
|
|
domain label starting and ending with an alphanumerical character
|
|
and possibly also containing "-" characters. The rightmost domain
|
|
label will never start with a digit. Domain names are not case
|
|
sensitive.
|
|
|
|
REMOTE_HOST = "" | hostname
|
|
hostname = *( domainlabel ".") toplabel
|
|
domainlabel = alphadigit [ *alphahypdigit alphadigit ]
|
|
toplabel = alpha [ *alphahypdigit alphadigit ]
|
|
alphahypdigit = alphadigit | "-"
|
|
alphadigit = alpha | digit
|
|
|
|
REMOTE_IDENT
|
|
|
|
The identity information reported about the connection by a RFC <./rfc931>
|
|
931 <./rfc931> [10 <#ref-10>] request to the remote agent, if available. The server may
|
|
choose not to support this feature, or not to request the data for
|
|
efficiency reasons.
|
|
|
|
REMOTE_IDENT = *CHAR
|
|
|
|
The data returned is not appropriate for use as authentication
|
|
information.
|
|
|
|
REMOTE_USER
|
|
|
|
This variable is specific to requests made with HTTP.
|
|
|
|
If AUTH_TYPE is "Basic", then the user-ID sent by the client. If
|
|
AUTH_TYPE is NULL, then NULL, otherwise undefined.
|
|
|
|
REMOTE_USER = "" | userid | *OCTET
|
|
userid = token
|
|
|
|
REQUEST_METHOD
|
|
|
|
This variable is specific to requests made with HTTP.
|
|
|
|
|
|
|
|
Robinson [Page 10]
|
|
|
|
<#page-11>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
The method with which the request was made, as described in
|
|
section 5.1.1 <#section-5.1.1> of the HTTP/1.0 specification [3 <#ref-3>].
|
|
|
|
REQUEST_METHOD = http-method
|
|
http-method = "GET" | "HEAD" | "POST" | extension-method
|
|
extension-method = token
|
|
|
|
The method is case sensitive.
|
|
|
|
SCRIPT_NAME
|
|
|
|
A URL path that could identify the CGI script (rather then the
|
|
particular CGI output). The syntax and semantics are identical to
|
|
a decoded HTTP URL `hpath' token [4 <#ref-4>].
|
|
|
|
SCRIPT_NAME = "" | "/" [ path ]
|
|
|
|
The leading "/" is not part of the path. It is optional if the
|
|
path is NULL.
|
|
|
|
The SCRIPT_NAME string is some leading part of the <path>
|
|
component of the script URI derived in some implementation defined
|
|
manner.
|
|
|
|
SERVER_NAME
|
|
|
|
The name for this server, as used in the <host> part of the script
|
|
URI. Thus either a fully qualified domain name, or an IP address.
|
|
|
|
SERVER_NAME = hostname | hostnumber
|
|
|
|
SERVER_PORT
|
|
|
|
The port on which this request was received, as used in the <port>
|
|
part of the script URI.
|
|
|
|
SERVER_PORT = 1*digit
|
|
|
|
SERVER_PROTOCOL
|
|
|
|
The name and revision of the information protocol this request
|
|
came in with.
|
|
|
|
SERVER_PROTOCOL = HTTP-Version | extension-version
|
|
HTTP-Version = "HTTP" "/" 1*digit "." 1*digit
|
|
extension-version = protocol "/" 1*digit "." 1*digit
|
|
protocol = 1*( alpha | digit | "+" | "-" | "." )
|
|
|
|
|
|
|
|
|
|
Robinson [Page 11]
|
|
|
|
<#page-12>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
`protocol' is a version of the <scheme> part of the script URI,
|
|
and is not case sensitive. By convention, `protocol' is in upper
|
|
case.
|
|
|
|
SERVER_SOFTWARE
|
|
|
|
The name and version of the information server software answering
|
|
the request (and running the gateway).
|
|
|
|
SERVER_SOFTWARE = *CHAR
|
|
|
|
|
|
6 <#section-6>. Invoking the script
|
|
|
|
|
|
|
|
This script is invoked in a system defined manner. Unless specified
|
|
otherwise, this will be by treating the file containing the script as
|
|
an executable, and running it as a child process of the server.
|
|
|
|
|
|
7 <#section-7>. The CGI script command line
|
|
|
|
|
|
|
|
Some systems support a method for supplying a array of strings to the
|
|
CGI script. This is only used in the case of an `indexed' query. This
|
|
is identified by a "GET" or "HEAD" HTTP request with a URL search
|
|
string not containing any unencoded "=" characters. For such a
|
|
request, the server should parse the search string into words, using
|
|
the rule:
|
|
|
|
search-string = search-word *( "+" search-word )
|
|
search-word = 1*schar
|
|
schar = xunreserved | escape | xreserved
|
|
xunreserved = alpha | digit | xsafe | extra
|
|
xsafe = "$" | "-" | "_" | "."
|
|
xreserved = ";" | "/" | "?" | ":" | "@" | "&"
|
|
|
|
After parsing, each word is URL-decoded, optionally encoded in a
|
|
system defined manner and then the argument list is set to the list
|
|
of words.
|
|
|
|
If the server cannot create any part of the argument list, then the
|
|
server should generate no command line information. For example, the
|
|
number of arguments may be greater than operating system or server
|
|
limitations, or one of the words may not be representable as an
|
|
argument.
|
|
|
|
|
|
8 <#section-8>. Data input to the CGI script
|
|
|
|
|
|
|
|
As there may be a data entity attached to the request, there must be
|
|
a system defined method for the script to read this data. Unless
|
|
defined otherwise, this will be via the `standard input' file
|
|
|
|
|
|
|
|
Robinson [Page 12]
|
|
|
|
<#page-13>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
descriptor.
|
|
|
|
There will be at least CONTENT_LENGTH bytes available for the script
|
|
to read. The script is not obliged to read the data, but it must not
|
|
attempt to read more than CONTENT_LENGTH bytes, even if more data is
|
|
available.
|
|
|
|
For non-parsed header (NPH) scripts (see below), the server should
|
|
attempt to ensure that the script input comes directly from the
|
|
client, with minimal buffering. For all scripts the data will be as
|
|
supplied by the client.
|
|
|
|
|
|
9 <#section-9>. Data output from the CGI script
|
|
|
|
|
|
|
|
There must be a system defined method for the script to send data
|
|
back to the server or client; a script will always return some data.
|
|
Unless defined otherwise, this will be via the `standard output' file
|
|
descriptor.
|
|
|
|
There are two forms of output that the script can give; non-parsed
|
|
header (NPH) output, and parsed header output. A server is only
|
|
required to support the latter; distinguishing between the two types
|
|
of output (or scripts) is implementation defined.
|
|
|
|
|
|
9.1 <#section-9.1>. Non-Parsed Header Output
|
|
|
|
|
|
|
|
The script must return a complete HTTP response message, as described
|
|
in Section 6 <#section-6> of the HTTP specification [3 <#ref-3>]. Note that this allows an
|
|
HTTP/0.9 response to an HTTP/1.0 request.
|
|
|
|
The server should attempt to ensure that the script output is sent
|
|
directly to the client, with minimal buffering.
|
|
|
|
|
|
9.2 <#section-9.2>. Parsed Header Output
|
|
|
|
|
|
|
|
The script returns a CGI response message.
|
|
|
|
CGI-Response = *( CGI-Header | HTTP-Header ) NL [ Entity-Body ]
|
|
CGI-Header = Content-type
|
|
| Location
|
|
| Status
|
|
| extension-header
|
|
|
|
The response comprises headers and a body, separated by a blank line.
|
|
The headers are either CGI headers to be interpreted by the server,
|
|
or HTTP headers to be included in the response returned to the client
|
|
if the request method is HTTP. At least one CGI-Header must be
|
|
supplied, but no CGI header can be repeated with the same field-name.
|
|
|
|
|
|
|
|
Robinson [Page 13]
|
|
|
|
<#page-14>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
If a body is supplied, then a Content-type header is required,
|
|
otherwise the script must send a Location or Status header. If a
|
|
Location header is returned, then no HTTP-Headers may be supplied.
|
|
|
|
The CGI headers have the generic syntax:
|
|
|
|
generic-header = field-name ":" [ field-value ] NL
|
|
field-name = 1*<any CHAR, excluding CTLs, SP and ":">
|
|
field-value = *( field-content | LWSP )
|
|
field-content = *( token | tspecial | quoted-string )
|
|
|
|
The field-name is not case sensitive; a NULL field value is
|
|
equivalent to the header not being sent.
|
|
|
|
Content-Type
|
|
|
|
The Internet Media Type [9 <#ref-9>] of the entity body, which is to be
|
|
sent unmodified to the client.
|
|
|
|
Content-Type = "Content-Type" ":" media-type NL
|
|
|
|
Location
|
|
|
|
This is used to specify to the server that the script is returning
|
|
a reference to a document rather than an actual document.
|
|
|
|
Location = "Location" ":"
|
|
( fragment-URI | rel-URL-abs-path ) NL
|
|
fragment-URI = URI [ # fragmentid ]
|
|
URI = scheme ":" *qchar
|
|
fragmentid = *qchar
|
|
rel-URL-abs-path = "/" [ hpath ] [ "?" query-string ]
|
|
hpath = fpsegment *( "/" psegment )
|
|
fpsegment = 1*hchar
|
|
psegment = *hchar
|
|
hchar = alpha | digit | safe | extra
|
|
| ":" | "@" | "& | "="
|
|
|
|
The location value is either an absolute URI with optional
|
|
fragment, as defined in RFC 1630 <./rfc1630> [1 <#ref-1>], or an absolute path and
|
|
optional query-string. If an absolute URI is returned by the
|
|
script, then the server will generate a redirect HTTP response
|
|
message, and if no entity body is supplied by the script, then the
|
|
server will produce one. If the Location value is a path, then the
|
|
server will generate the response that it would have produced in
|
|
response to a request containing the URL
|
|
|
|
protocol "://" SERVER_NAME ":" SERVER_PORT rel-URL-abs-path
|
|
|
|
|
|
|
|
Robinson [Page 14]
|
|
|
|
<#page-15>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
The location header may only be sent if the REQUEST_METHOD is HEAD
|
|
or GET.
|
|
|
|
Status
|
|
|
|
The Status header is used to indicate to the server what status
|
|
code it will use in the response message. It should not be sent if
|
|
the script returns a Location header.
|
|
|
|
Status = "Status" ":" 3digit SP reason-phrase NL
|
|
reason-phrase = *<CHAR, excluding CTLs, NL>
|
|
|
|
The valid status codes are listed in section 6.1.1 <#section-6.1.1> of the HTTP/1.0
|
|
specification [3 <#ref-3>]. If the script does not return a Status header,
|
|
then "200 OK" should be assumed.
|
|
|
|
HTTP headers
|
|
|
|
The script may return any other headers defined by the HTTP/1.0
|
|
specification [3 <#ref-3>]. The server must translate the header data from
|
|
the CGI header syntax to the HTTP header syntax if these differ.
|
|
For example, the character sequence for newline (such as Unix's
|
|
ASCII NL) used by CGI scripts may not be the same as that used by
|
|
HTTP (ASCII CR followed by LF). The server must also resolve any
|
|
conflicts between headers returned by the script and headers that
|
|
it would otherwise send itself.
|
|
|
|
|
|
10 <#section-10>. Requirements for servers
|
|
|
|
|
|
|
|
Servers must support the standard mechanism (described below) which
|
|
allows the script author to determine what URL to use in documents
|
|
which reference the script. Specifically, what URL to use in order to
|
|
achieve particular settings of the environment variables. This
|
|
mechanism is as follows:
|
|
|
|
The value for SCRIPT_NAME is governed by the server configuration and
|
|
the location of the script in the OS file-system. Given this, any
|
|
access to the partial URL
|
|
|
|
SCRIPT_NAME extra-path ? query-information
|
|
|
|
where extra-path is either NULL or begins with a "/" and satisfies
|
|
any other server requirements, will cause the CGI script to be
|
|
executed with PATH_INFO set to the decoded extra-path, and
|
|
QUERY_STRING set to query-information (not decoded).
|
|
|
|
Servers may reject with error 404 any requests that would result in
|
|
an encoded "/" being decoded into PATH_INFO or SCRIPT_NAME, as this
|
|
|
|
|
|
|
|
Robinson [Page 15]
|
|
|
|
<#page-16>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
might represent a loss of information to the script.
|
|
|
|
Although the server and the CGI script need not be consistent in
|
|
their handling of URL paths (client URLs and the PATH_INFO data,
|
|
respectively), server authors may wish to impose consistency. So the
|
|
server implementation should define its behaviour for the following
|
|
cases:
|
|
|
|
o define any restrictions on allowed characters, in particular
|
|
whether ASCII NULL is permitted;
|
|
|
|
o define any restrictions on allowed path segments, in particular
|
|
whether non-terminal NULL segments are permitted;
|
|
|
|
o define the behaviour for "." or ".." path segments; i.e. whether
|
|
they are prohibited, treated as ordinary path segments or
|
|
interpreted in accordance with the relative URL specification
|
|
[7 <#ref-7>];
|
|
|
|
o define any limits of the implementation, including limits on
|
|
path or search string lengths, and limits on the volume of
|
|
headers the server will parse.
|
|
|
|
Servers may generate the script URI in any way from the client URI,
|
|
or from any other data (but the behaviour should be documented).
|
|
|
|
|
|
11 <#section-11>. Recommendations for scripts
|
|
|
|
|
|
|
|
Scripts should reject unexpected methods (such as DELETE etc.) with
|
|
error 405 Method Not Allowed. If the script does not intend
|
|
processing the PATH_INFO data, then it should reject the request with
|
|
404 Not Found if PATH_INFO is not NULL.
|
|
|
|
If the output of a form is being processed, check that CONTENT_TYPE
|
|
is "application/x-www-form-urlencoded" [2 <#ref-2>].
|
|
|
|
If parsing PATH_INFO, PATH_TRANSLATED or SCRIPT_NAME then be careful
|
|
of void path segments ("//") and special path segments ("." and
|
|
".."). They should either be removed from the path before use in OS
|
|
system calls, or the request should be rejected with 404 Not Found.
|
|
It is very unlikely that any other use could be made of these.
|
|
|
|
As it is impossible for the script to determine the client URI that
|
|
initiated this request without knowledge of the specific server in
|
|
use, the script should not return text/html documents containing
|
|
relative URL links without including a <BASE> tag in the document.
|
|
|
|
When returning headers, the script should try to send the CGI headers
|
|
|
|
|
|
|
|
Robinson [Page 16]
|
|
|
|
<#page-17>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
as soon as possible, and preferably before any HTTP headers. This may
|
|
help reduce the server's memory requirements.
|
|
|
|
|
|
12 <#section-12>. System specifications
|
|
|
|
|
|
|
|
12.1 <#section-12.1>. AmigaDOS
|
|
|
|
|
|
|
|
Environment variables
|
|
|
|
These are accessed by the DOS library routine GetVar. The flags
|
|
argument should be 0. Case is ignored, but upper case is
|
|
recommended for compatibility with case-sensitive systems.
|
|
|
|
The current working directory
|
|
|
|
The current working directory for the script is set to the
|
|
directory containing the script.
|
|
|
|
Character set
|
|
|
|
The US-ASCII character set is used for the definition of
|
|
environment variables and headers; the newline (NL) sequence is CR
|
|
LF.
|
|
|
|
|
|
12.2 <#section-12.2>. Unix
|
|
|
|
|
|
|
|
For Unix compatible operating systems, the following are defined:
|
|
|
|
Environment variables
|
|
|
|
These are accessed by the C library routine getenv.
|
|
|
|
The command line
|
|
|
|
This is accessed using the the argc and argv arguments to main().
|
|
The words are have any characters which are `active' in the Bourne
|
|
shell escaped with a backslash.
|
|
|
|
The current working directory
|
|
|
|
The current working directory for the script is set to the
|
|
directory containing the script.
|
|
|
|
Character set
|
|
|
|
The US-ASCII character set is used for the definition of
|
|
environment variables and headers; the newline (NL) sequence is
|
|
LF; servers should also accept CR LF as a newline.
|
|
|
|
|
|
|
|
Robinson [Page 17]
|
|
|
|
<#page-18>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
13 <#section-13>. Security Considerations
|
|
|
|
|
|
|
|
13.1 <#section-13.1>. Safe Methods
|
|
|
|
|
|
|
|
As discussed in the security considerations of the HTTP specification
|
|
[3 <#ref-3>], the convention has been established that the GET and HEAD
|
|
methods should be `safe'; they should cause no side-effects and only
|
|
have the significance of resource retrieval.
|
|
|
|
|
|
13.2 <#section-13.2>. HTTP headers containing sensitive information
|
|
|
|
|
|
|
|
Some HTTP headers may carry sensitive information which the server
|
|
should not pass on to the script unless explicitly configured to do
|
|
so. For example, if the server protects the script using the Basic
|
|
authentication scheme, then the client will send an Authorization
|
|
header containing a username and password. If the server, rather than
|
|
the script, validates this information then it should not pass on the
|
|
password via the HTTP_AUTHORIZATION environment variable.
|
|
|
|
|
|
13.3 <#section-13.3>. Script interference with the server
|
|
|
|
|
|
|
|
The most common implementation of CGI invokes the script as a child
|
|
process using the same user and group as the server process. It
|
|
should therefore be ensured that the script cannot interfere with the
|
|
server process, its configuration or documents.
|
|
|
|
If the script is executed by calling a function linked in to the
|
|
server software (either at compile-time or run-time) then precautions
|
|
should be taken to protect the core memory of the server, or to
|
|
ensure that untrusted code cannot be executed.
|
|
|
|
|
|
14 <#section-14>. Acknowledgements
|
|
|
|
|
|
|
|
This work is based on the original CGI interface that arose out of
|
|
discussions on the www-talk mailing list. In particular, Rob McCool,
|
|
John Franks, Ari Luotonen, George Phillips and Tony Sanders deserve
|
|
special recognition for their efforts in defining and implementing
|
|
the early versions of this interface.
|
|
|
|
This document has also greatly benefited from the comments and
|
|
suggestions made Chris Adie, Dave Kristol and Mike Meyer.
|
|
|
|
|
|
15 <#section-15>. References
|
|
|
|
|
|
|
|
[1] Berners-Lee, T., `Universal Resource Identifiers in WWW: A
|
|
Unifying Syntax for the Expression of Names and Addresses of
|
|
Objects on the Network as used in the World-Wide Web', RFC 1630 <./rfc1630>,
|
|
CERN, June 1994.
|
|
|
|
|
|
|
|
Robinson [Page 18]
|
|
|
|
<#page-19>
|
|
INTERNET-DRAFT Common Gateway Interface - 1.1 15 February 1996
|
|
|
|
|
|
[2] Berners-Lee, T. and Connolly, D., `Hypertext Markup Language -
|
|
2.0', RFC 1866 <./rfc1866>, MIT/W3C, November 1995.
|
|
|
|
[3] Berners-Lee, T., Fielding, R. T. and Frystyk Nielsen, H.,
|
|
`Hypertext Transfer Protocol -- HTTP/1.0', Work in progress
|
|
(draft-ietf-http-v10-spec-04.txt <./draft-ietf-http-v10-spec-04.txt>), MIT/LCS, UC Irvine, October
|
|
1995.
|
|
|
|
[4] Berners-Lee, T., Masinter, L. and McCahill, M., Editors,
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`Uniform Resource Locators (URL)', RFC 1738 <./rfc1738>, CERN, Xerox
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Corporation, University of Minnesota, December 1994.
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[5] Braden, R., Editor, `Requirements for Internet Hosts --
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Application and Support', STD 3, RFC 1123 <./rfc1123>, IETF, October 1989.
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[6] Crocker, D.H., `Standard for the Format of ARPA Internet Text
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Messages', STD 11, RFC 822 <./rfc822>, University of Delaware, August 1982.
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[7] Fielding, R., `Relative Uniform Resource Locators', RFC 1808 <./rfc1808>, UC
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Irving, June 1995.
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[8] Mockapetris, P., `Domain Names - Concepts and Facilities', STD
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13, RFC 1034 <./rfc1034>, ISI, November 1987.
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[9] Postel, J., `Media Type Registration Procedure', RFC 1590 <./rfc1590>, ISI,
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March 1994.
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[10] StJohns, M., `Authentication Server', RFC 931 <./rfc931>, TPSC, January
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1985.
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[11] `Coded Character Set -- 7-bit American Standard Code for
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Information Interchange', ANSI X3.4-1986.
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16 <#section-16>. Author's Address
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David Robinson
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Institute of Astronomy
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University of Cambridge
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Madingley Road
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Cambridge CB3 0HA
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UK
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Tel: +44 (1223) 337528
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Fax: +44 (1223) 337523
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EMail: drtr@ast.cam.ac.uk
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Robinson [Page 19]
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Html markup produced by rfcmarkup 1.107, available from
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http://tools.ietf.org/tools/rfcmarkup/
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